Not better luck with the Z2.
The sound and the video are just great, I would say the sound for my taste that is better than the sony A-865, the video way superior since is capable of 1080p, I only watched 720p movies though. The battery life also better than the Sony Walkman, no much but definitely better.
The control buttons are not very easy to use, I prefer Sony A865 and better yet the Cowon J3.
Well but not everything is perfect, Cowon Z2 is a very weak android phone, very poor wi-fi connection, many times while downloading an app from the Goggle play Market (which I installed easily following the instruction also given in head-fi) the connection went down, I could installed some app. like Powe-ramp which works better than the default player which does not even show the proper cover albums, I did have the latest firmware, but the problem still persists.
When running apps. the Z2 crashed several times even with very basic app. like Brightness Level.
The blue-tooth would fail during transferring files.
Summarizing, the sound and video are very good, but for an Android device my actual basic Samsung Galaxy Gio S5660 performs much better than the Z2, even when I use Poweramp in my phone there is not much difference between them, cowon Z2 is still better but is very subtle difference, I realized that using my Android phone I get very similar sound, however, the battery would drain quite quickly since I need the volume almost at the max level with my ATH-m50, but I just charge it a bit more often. I believe there is no point in expending the money in a Cowon Z2 when does not perform as It should (as an android device) so I sent it back; and for now I will just use my Galaxy Gio with Power-amp until a pmp like Cowon J3 but improved (more video support and better blue-tooth) could be released in the market. I think Cowon J3 was the pmp to have (great audio support and battery life), hopefully cowon could put in the market a new model following that line, then I would consider again getting a Pmp, however how things are moving, my next pmp could be just a new Android Phone with a great battery life, nice screen like Amoled and that should be enough, I read that Sharp is releasing a new Phone (Sharp AQUOS PHONE SH-07D) with a great battery life for music and a Wolfson dac like Cowon (there are others phones with Wolfson Dac and Yamaha but without a great battery), still it seems very expensive but that could be the way.
For now I will wait for a while to see what happens in the market.